106 



THE AMERICAN ENTOMOLOGIST. 



cous-white pubescence. The larva ret^ides in 

 the very heart of the gall, as with the other spe- 

 cies, but instead of the cocoon beinof thrice as 

 long as the body of the larva, it is scarcely at all 

 longer, and fits so closely that it is not a very easj; 

 matter to remove it. In these two species, the 

 larva and pupa of one are absolutely undistin- 

 guishable from those of the other, and the perfect 

 flies resemble one another so closely that the 

 same figure answers equally well for both. 

 Their transformations also take place in the same 

 manner and very nearly at the same time; and 

 the galls attain tlicir full growth in tlic same 

 month of July. 



The Gu,u-e-Vine Ai-i'i.k-g.u.l, (Vitii po- 

 mum, new species.) Fig. 8.3 a. — In No. 2, page 

 28, and Xo. .'!, page 64, of the American E\to- 

 MOLOGIST, we referred to a "vegetable phenom- 

 enon" said to be found in Virginia, in the form 

 of an applee-like growth from a grape-vine. The 

 prevailing opinion in that State seemed to be, 

 that it was a kind of hybrid fruit formed by the 

 union of a grape blossom with an apple 

 blossom. But we intimated our opinion at 

 the time, that it was no fruit at all, but 

 simply a gall produced by some nnknown 

 species of gall gnat. "We have since received 

 specimens of what is undoubtedly the same 

 tiling, from two dift'erent .sources, first from Mr. 

 I>. L. Kingsbury of Alton, Illinois, and second 

 through the kindness of Mr. Stauflfer, of Penn- 

 sylvania, from Thos. Median, the well known 

 editor of the Gardeners' Monthly. Mr. StanfTer 

 has also favored us with a good colored figure of 

 one that he cut from the wild Frost Grape ( Vitis 

 rordifoUa) , August 0th, 1850, which agrees per- 

 fectly well with the tv.-o specimens in our pos- 

 session. Hence, after carefully examining these 

 specimens, we can now announce with certainty 

 that this "vegetable phenomenon" is really what 

 wi' originally inferred it to be— namely, a g.all 

 made by a gall gnat. P'ig. 85 «, will give the reader 



been treating of, h.ave been what are technically 

 termed "monatlialamous" or "one-celled" galls, 

 inhabited by a single gall-making larva. But 

 this, as will be seen at once, is a "polythala- 

 mous" or many-celled gall, inhabited by a great 

 number of gall-making larvw. 



As the fly that generates this gall will, in all 

 probability, not make its appearance until next 

 spring or summer, and as we have consequently 

 had, as yet, no opportunity to breed it; it may 

 be very reasonably asked, how we know forcer- 

 tain that it will turn out to be some kind of Gall- 

 gnat {Cecidomyla)'i We answer thatthelarva?of 

 all Gall-gnats are distinguishable at once from 

 other larvic by a peculiar process known as 

 the "breast-bone," and located on thelower sur- 

 face of the first joint of the breast. (See Fig. 86, 

 c.) Usually this "breast-bone" is of so dark a 

 color that it can be readily seen, even in a very 

 small larva, and its use apparently is to abrade 

 the surface upon which the larva lives and there- 

 by cause an abnoi-nial flow of sap, which forms 

 the food of the little insect that is thus working 

 for its living. In Figure 86, r, the head of the lar- 

 va is shown protruded ; but all this group of larva^ 

 have the power of retracting the head within the 

 body, so as to bring the "breast-bone" well into 

 play. In shape, this organ differs greatly, being 

 sometimes what we have called "clove-shaped," 

 as in Fig. 86, c, sometimes Y-shaped, as with 

 the larvaj of the two Willow-galls figured above, 

 and sometimes of other allied shapes. But in 

 cver>- case there arc several sharp prongs in front 

 of it, adapted for wounding and piercing. As 

 a general rule, allied gall-gnats iidrabiting the 

 same genus of plants have larva" with "breast- 

 bones" of the same, or a very similar shape. 

 For example, that of the larva to be next des- 

 cribed is absolutely undistinguishablc from that 

 of our larva; and so is that of the larva of the 

 Pine-cone gall from lluii of Ihc hirvii nf (lie C-ih- 

 bage-sprout g.all.* 



TiTi- r:>7ii-f.i-ivr 1,'ir U1.I/T..;*! 1 ( t7/;.< r-r,)W/. 



/ —^\^ h ^e n t \Mth int oi 



a very good idea of this gall, and Fig. 85, b, ( f 

 its internal structure, showing the larvic that in 

 habit its numerous cells, a single larva in a sin 

 gle cell. All the galls that wo have hitherto 



■9 li e 

 mo tl 



